Self feeding carburetor



April 27, 1937. w. o. CHASE 2,078,901

SELF FEEDING CARBURETOR Original Filed June 50, 1954 5 Sheets-Sheet 1 6? BY j April 27, 1937. W o, HA E 2,078,901

SELF FEEDING CARBURETOR Original Filed June 30, 1954 5 Sheets-Sheet 2 INVENTOR.

ATTORNEY.

p 37- I W. O.CI-IASE 2,078,901

SELF FEEDING CARBURETQR Original Filed June 30, 1934 3 Sheets-Sheet 3 I IIIII IH I. III

I IIIIIII II BY M I i ATTORNEY.-

Patented Apr. 27, 1937 PATENT orifice SELF FEEDING CARBURETOR Wilfred 0. Chase, Detroit, Mich.

Application June 30, 1934, Serial No. 733,215 Renewed October 10, 1936 23 Claims.

The object of this invention is to make a carburetor in which the fuel is automatically raised to the fuel nozzle without the use of a fuel pump. In other words, a carburetor of the type generally known in the trade as a self feeding carburetor. v

Fig. 1 shows a cross sectional elevation on the plane l--l of Fig. 2

Fig. 2 is an outside elevation of the carburetor.

Fig. 3 is'a modified view of a portion of Fig. 1 showing the position of the moving parts when the throttle is in the wide open position.

Fig. 4 is a partial cross sectional plan view on the plane l-t of Fig. 1. V

'Fig. 5 is a cross sectional plan View on plane 5--5 of Fig. l. V

Fig. 6 is 'a cross sectional plan view taken on plane 66 of Fig. l.

Fig. '7 shows diagrammatically in elevation the principal fuel and air passages in the carburetor.

Description Considering first Figure 7, the air entrance Ii in the carburetor body {93, is shown controlled by an air valve !2. This air valve floats in the air stream and engages with the lip B5 of the fuel outlets 35 and 34 which are connected together through a cross passage 33. The valve 12 is guided in a cylinder l3 which is supported by arms M in the air entrance H. A disc l5 supported on a rod 16 is guided inside the cylinder Hand on the rod l6 engaged with theair valve 12. The shoulder ll engages with the arm !8 of a lever 19 supported ona pivot 26 and thus gives a manually operated control for either limiting the opening or completely closing the air entrance between the lip Hi5 and the cylinder valve l2. The air valve as stated above is arranged to float in the air stream, the means whereby it floats comprising a rod 2!, a disc 22 and a disc 23. These two discs move in tapered fuel passages 24 and 25. Fuel is supplied to the upper tapered fuel passage 24 by means of the horizontal passage 4"? located in a bridge t9 in a the main air-passage. This horizontal fuel passage 41 obtains its fuel from the fuel chamber 67, through the fuel passage 4i and past the spring check valve B5, which is spring loaded. The fuel passage 4:"! communicates through a small passage 19 with the upper part of the fuel chamber between the passages 11 and ll. There is a lower passage38 for mixed-air and; fuel communicating leading to the passage 38. This tapered valve 13 is supported on a flexible diaphragm it! which in its turn is supported on a coil spring 68 in a spring retainer 69 and located in the fuel chamber 61. Concentric with the tapered valve '13 which is guided in the plug 14 is another valve 86 which acts as a cut-off valve between a fuel passage t5 and the fuel chamber 61. This fuel passage obtains its fuel through pipe 9i (Fig. 2) from a fuel tank at a lower level commonly known as a fuel tank of a car. Atmospheric pressure is applied on an upper portion of the diaphragm ill through a small opening Ill in the cover over the diaphragm 10, which cover is held in place by screws 94.

Low speed fuel supply passages are provided which connect the fuel passage 41 (see Fig. l) to the passage 28 controlled'by an adjustable screw plug 21. The passage 28 discharges into the mixture outlet on the engine side of throttle 3i through opening 3|]. The main running mixture is obtained from the air flowing through the entrance I l and the fuel which flows beneath the lip H15 and then mixes with the air flowing past the air valve 12. This mixture passes down both sides of thebridge 99 in which. is located the passages 26 and 31 and so through the mixture chamber I00 to the engine side of the throttle valve 3 l The carburetor is adapted to be bolted to an inlet manifold not shown by means of aflange 92.

In the carburetor as actually made, it has been found necessary to add a few extra parts as shown in Figures 1 to 6. Describing the carburetor as illustratedin Figures 1 to 6; with particular reference to the various control parts added, Ill is the air entrance which provides air which flows by the floating air valve l2, guided in the cylinder it which is supported by the arm it in said air entrance ll. This air valve controls the fuel issuing from the fuel passages E i and 35 under the lip I05 which acts as a spreader for the fuel entering the air stream. The disc 15 controlled by a shaft it enables the air valve 1-2 to be closed by a manually controlled lever is supported on the shaft 20 engaging through an arm It with a shoulder ll mounted on a shaft it. For obvious reasons the disc I5 is provided with passage 5! perforations I5. The floating air valve I2 is guided on the shaft 2! which carries the two discs 22 and 23 which float in the tapered fuel passages 24 and 25. The fuel passage 26 communicates through the passage All with the horizontal passage 46 which in its turn communicates with the annular tapered passage 15 lo cated in the movable piston lfil. Fuel flows from the fuel chamber 67 through the outlet 66 past the check valve 65 thru the passage ll to the piston I01 past the check valve 42 which rests on the annular seat 43. The check valve is controlled by the spring 6d and guided in the screw plug 62 by means of the guide 63. Two openings :34 in the piston lfll allow fuel to flow into the tapered passage 35. The fuel flows also to the upper part of the cylinder in which this piston IOI reciprocates through the piston lill in which passages are provided, and escapes from the upper part of the cylinder through a plug I03 which is provided with passages, specifically with the passage 59 which communicates with the passage 55 in the plug Hi3 which discharges into the annular passage 54 and clearance chamber 52 which in its turn communicates with the passage 53 which leads to a passage 5!, which also communicates with the passage 26.

The plug N13 is also provided with the passage 56 which communicates through a chamber 5'5 and a passage 58 with the air entrance 5!. These passages 56 are also in communication with the fuel passages 55 and the annular passage 54. In this arrangement the passage 55 can either supply fuel to 26 or supply air as the case may be. Referring to Figure 5, will be noticed that there is a passage leading around the cylinder in which the piston Hill reciprocates. This passage is numbered l8d9 and communicates through a passage 58 with the vertical cylindrical passage Ml which is in alignment with and a continuation of the cylinder IM. This passage 40 is controlled by a piston valve in the form of a tapered plug 40'. The passage 49 and I04 communicates with the horizontal passage l5 which in its turn communicates with the passage controlled by the tapered plug 73 which is guided in the cap M. The orifice controlled by the tapered plug 13 is numbered 12 and the air flow through the restricted opening I2 is obtained by the passage H which communicates with the air entrance l!;. A bypass air passage 16 is provided leading from the horizontal air passage T5 to the lower portion of the vertical passage 30. The second tapered fuel passage 25 in the bridge 58 across the air inlet ll communicates through a horizontal passage 37 through another horizontal passage 38 (see Figure 6), 38 through a passage 39 with the lower portion of the vertical passage 40.

The fuel supply for the engine is obtained through the large opening 85 which communicates with the fuel tank, not shown. The fuel flows by the shut-off valve 85 which is suspended in the fuel entrance 85 and is controlled by a flexible diaphragm l8. This flexible diaphragm 1i] is supported by a coil spring 68 located around the tube 89 which has an outlet opening M. A fuel entrance 8'! is provided which Widens out into a fuel passage 88 inside the fuel tube 89 so that the fuel can flow through :38 into the fuel chamber 61. The flexible diaphragm i6 is arranged beneath the wall 93 which creates the chamber H)? which communicates with the atmosphere through the opening HI. The piston l0! which not only serves as a fuel path but also as an accelerating pump is operated by a rod I82, through the fork connection 82, connected by a link 80 to the throttle rod carrying the valve 31 by means of the throttle lever I09 and a pin connection. The pin 8| which goes through the fork and link 80 is also pivotally connected to the rod 84 which has a perforated boss 83. This rod 84 controls the piston 40 which is adapted to reciprocate in the cylinder d0. Air reaches the lower part of the cylinder Gil through the bypass passage 16. The piston 40' thus serves to alternatively connect the air entrance ll through a passage 'H past the tapered needle 13 and the restrict-ed opening 12 with the air fuel passage 'l5'l64839 (see Fig. 6) and through the air fuel passage 15-404 with the passage 5ll4948 and 26 (see Figure 5), both passages communicate with the cross passage 33 which discharges through 34-35 under the annulus beneath the lip I95.

A vapor outlet consisting of an opening 11, a check valve 18 and a passage 19 which communicates with the fuel passage ll is provided so that the flow of fuel down 4| allows the vapor to be drawn from the upper part of 61 immediately beneath the diaphragm 10. The atomizing air for low speed flows down l5l04, past the tapered control valve 36 across the passage 50, along the passage 49 across the passage 48 to the passage 26 (see Figure 5) where fuel is admitted from the passage 5!. Low speed fuel and air then flows past adjustable screw plug 21 down.

passage 28 to the mixture outlet on the engine side of the throttle 3i, passing through the passage 29 to the low speed fuel outlet 30.

Operation To start the engine it is assumed that the throttle is opened from the position as shown in Figure 2. In this position the choke lever I9 is raised so as to hold the air valve l2 down on its seat M5 by means of the disc I5. Engine suction then acts through 34 and 35 and communicates through the various gasoline passages with the underside of the diaphragm l0. Atmospheric pressure which enters through Ill into the air chamber I91 presses the diaphragm down and thus unseats the shut-off valve 86. Gasoline then flows up the gasoline passages 8l88 out of the passage 90 into the gasoline chamber 61. The check valve is unseated and gasoline flows down A! past the gasoline check valve 42 and through the gasoline passages 44 and 45, along it, up 41, along 26 and so into the tapered opening 2 where it raises the disc 22 which is mounted on the rod 2| which, of course, supports and raises the air valve [2 once the choke valve lever I9 is pushed down so as to release the air valve :2 and to permit it to float in the air stream. Immediately after the engine fires the lever I9 is pushed down and the valve [2 then floats in the air stream, the opening being determined by the gasoline flow by the disc 22. Air is mingled with the fuel in 26 this air being derived from the opening 72 and the passage 50 (see Figure 5) and also from the opening 58 and passage 5|. When the throttle is opened the opening connecting 5i with the air passage I 04 and 40 is shut off because the piston valve 40' is raised by the rod 84 mounted on the rod 8| which is connected to lever I09 through the link air then enters 39 from the air passage 16. This air is admitted to the air passage 31 (see Figure 6) and air is thus admitted beneath the disc 23. This air tends to cause the disc 23 to float up and to carry with it the air valve I2. This insures an adequate air opening between the annular air valve I2 and the annular fuel orificewhich is formed by the inclined lip I05. When the throttle is opened, air flows past the tapered valve 13 to the fuel nozzles 34 and 35. At the same time a quantity of fuel is raised by the pumping action of the piston I0 I, the fuel caught above the check valve 42 being automatically raised and forced into the carburetor. This provides the fuel needed for accelerating and corresponds to the accelerating pumps that are now in universal use on all modern carburetors.

The fuel then flows not only out of passages 44 in the piston I0I but also out of passages 55 in the plugs I03 and 53 into the passage 5I communicating with passage 23 in the bridge 09 so that extra fuel is available for acceleration.

Normally when the throttle is in some fixed position fuel flows through passages 44 to passages 46-4'I-262434 and 35, and air flows down from the air entrance II through II past the air control valve 13 down either I04 or 16 to either 49 (see Figure 3) or 38 (see Figure 6) depending on whether the air control valve 40' is in the position shown in Fig. 1 or in the position shown in Fig. 3.

Correction for lift: The lift required to raise the fuel from the fuel tank to the fuel entrance 85 varies due to:

(a) variations in grade (1)) variations in level in the tank.

When there is a low level and/or a steep grade the pressure on the underside of the diaphragm is decreased and the valve "I3 is restricted because obviously when the fuel is low in the fuel tank or when the car is climbing a hill the level of fuel in the tank in each case is further below the level of the fuel at the fuel nozzle than it is when the car is driving on the level road with the fuel tank full.

This decrease in pressure under the diaphragm is communicated through the air and fuel passages I5-I0449-26 and also through the air and fuel passages -16-39-30 and 31 to the undersides of the discs 22 and 23. The tendency for the discs to rise in their conical passages 24 and 25 is due to the action of the mixture chamber suction acting on the upper surfaces of the discs22'23 through 34 and '35. This suction raises the valve I2 which controls the air entrance. Hence as the fuel lift increases the depression in the mixture outlet I00 also increases because the pressure on the underside of the discs '22 and 23 is restricted and hence the resistance to the rise of the air valve I2 is increased. Thus the suction created by the lift tends to hold the air valve shut, and to oppose the tendency .of the suction on the upper sides of the discs 2223 to raise the air valve I2. However, although this depression varies with the fuel lift it is necessary that the proportions of the mixture must not vary with the lift.

I have discovered that it is possible by varying the size of the vent I2 by means of the tapering needle I3, that I can maintain the mixture ratio practically constant. In addition to the level variations being used to control the air vent to the fuel nozzle, the throttle itself mechanically controls the admission of air. The additional air regulating means comprising the rod 84 and the tapered valve which alternatively puts the passage iiflancl thus passage 26 in communication with the passage I04 (see Figure 5) and puts the passage 39 and thus passage 31 in communication with the passage 10 (see Figure 6) gives the necessary variation in the mixture ratio so that a relatively rich mixture is available at wide open throttle. The function of the opening TI is to remove any vapor that may form in the upper chamber 61. The shut off valve 86 merely prevents fuel running out of 34 and 35 when the engine is not running in the event that the rear end of the car is raised so as to be higher than the carburetor. In this event the spring 00 will seat the valve 86 and prevent fuel flowing under gravity out of 34 and 35. The two check valves 65 and I8 cooperate to keep vapor out of the fuel chamber 61 and tomaintain it full of fuel.

When the engine is idling and .the throttle almost closed, the port 46 is also closed by the piston IIH and the fuel rises and flows through the passages 30 in the piston IOI passages in the plug I03 and so to port 53 in the plug I03, the idling fuel being mixed with air flowing down air passages 58, 51 and 56 from air inlet II. The mixed fuel and air flows down passage 5| to passage 23 and so past the idle regulating screw 21 down passage 38 through passage 29 to the outlet 30 in the mixture outlet. This ensures a steady flow past the check valve 42 in the piston IN, and it also ensures a full head of fuel up to the port 53 in the plug I03 and this fuel is available when the throttleis suddenly opened for acceleration. If the idle fuel was taken through passage 43 this fuel would not be available for acceleration. The shaft I02 is smaller than the hole through the plug I03 so that wear is not a factor to change the conditions of idling, as air flows down through the air passages 56 parallel to the clearance between the shaft I02 and the passage through which it is guided in I03.

I claim:

1. A fioatless self feeding carburetor for in ternal combustion engines comprising a cylindrical air valve, a primary air passage controlled thereby, a fuel supply passage leading thereto, a diaphragm responsive to the pressure in the fuel passage, a fuel outlet discharging into the air entrance on said engine side of the air valve and connected to said fuel supply passage, means responsive tothe velocity of flow in said fuel passage for controlling said air valve, valve means for admitting air to said fuel passage, said valve being operatively connected to said diaphragm for the purpose described.

2. A floatless self feeding carburetor comprising a primary air passage, a cylindrical air valve adapted to control said air entrance, 9. mixture chamber, a mixture outlet, a throttle valve therein, fuel supply means comprising a fuel chamber, a fuel entrance leading thereto, a fuel shut off valve in said fuel entrance, a diaphragm located in said fuel chamber and connected to said shut off valve, a fuel nozzle in said mixing chamber, a fuel passage leading from said fuel chamber to said fuel nozzle, means responsive to the flow of fuel in said fuel passage for controlling the movement of said air valve, valve means for admitting air to said fuel passage, said valve means being .operatively connected to said diaphragm.

3. In a carburetor as described in claim 2--an accelerating fuel pump located in the fuel passage leading from the fuel chamber to said fuel nozzle and operatively connected with said throttle.

4. A floatless self feeding carburetor comprising a cylindrical air valve, a primary air passage controlled thereby, a mixture chamber, a mixture outlet, fuel supply means comprising a fuel chamber, a fuel entrance leading thereto, a fuel shut off valve in said entrance, a diaphragm located in said fuel chamber and connected to said shut off valve, a fuel passage leading from said chamber to a fuel nozzle located in said mixing chamber, means responsive to the flow of fuel in said passage for controlling the movement of said air valve comprising a rod connected to said air valve, a conical passage, a disc adapted to move therein, said conical passage being located in the fuel passage leading from the fuel chamber to said fuel nozzle, valve means for admitting air to said fuel passage below said disc, said valve means being operatively connected to said diaphragm.

5. A floatless self feeding carburetor comprising a cylindrical air valve, an air entrance controlled thereby, a mixture chamber, a mixture outlet, fuel supply means comprising a fuel charnher, a fuel entrance leading thereto, a fuelshut off valve in said fuel entrance, a diaphragm located in said fuel chamber and connected to said shut off valve, two fuel passages leading from said fuel chamber to said mixing chamber, means responsive to the fiow of fuel in said fuel passages for controlling the movement of said air valve comprising a rod connected to said air valve, two discs located thereon, two conical fuel passages in which said discs reciprocate, said conical fuel passages being located one in each of said two fuel passages, valve means for admitting air to said fuel passages below said discs, said valve means being operatively connected to said dia-' phragm'.

6. A floatless self feeding carburetor comprising a cylindrical air valve, a primary air passage controlled thereby, a mixture chamber, a mixture outlet, a throttle valve therein, fuel supply means comprising a fuel chamber, a fuel entrance leading thereto, a fuel shut off valve in said fuel entrance, a diaphragm located in said fuel chamber and connected to said fuel shut off valve, two fuel passages leading from said fuel chamber to said mixing chamber, means responsive to the flow of fuel in said fuel passage for controlling the movement of said air valve comprising a rod connected to said air valve, two discs located thereon, two conical fuel passages in which said discs recipro cate, said conical fuel passages being located one in each of said two fuel passages, valve means for admitting air to said fuel passages below said discs, said valve means being operatively connected to said diaphragm, throttle controlled means for selectively directing said air alternately to one of said fuel passages for the purpose described.

7. In a fioatless self feeding carburetor for an internal combustion engine comprising an air valve, a primary air passage controlled thereby, a fuel entrance, a diaphragm responsive to the pressure in the fuel entrance, a fuel nozzle discharging into the air entrance on said engine side of the air valve, 3, fuel passage leading from the said fuel entrance to the said fuel nozzle, means responsive to the flow in said fuel passage for controlling said air valve, valve means for admitting air to said fuel passage, said valve being operatively connected to said diaphragm for the purpose described.

8. In a floatless self feeding carburetor, an air valve, a primary air passage controlled thereby, a fuel entrance, a mixture outlet, a throttle valve therein, a fuel nozzle discharging into the primary air passage on the outlet side of the said air valve, a cylinder, a piston therein operatively connected so as to be raised whenever the throttle is opened, a check valve in said piston, a fuel passage in said piston controlled by said valve, a fuel passage from the fuel entrance to the lower end of said cylinder, a fuel outlet in the lower portion of said cylinder, said fuel outlet being restricted by said piston when the throttle valve is closed, a second fuel outlet from the upper portion of said cylinder, an air passage leading from the atmosphere to said second fuel outlet, a common fuel passage into which both of said fuel outlets discharge, said common fuel passage communicating with said fuel nozzle.

9. Accelerating means for a fioatless self feeding carburetor having a mixture chamber, a mixture outlet, and a throttle therein, comprising a substantially vertical cylinder, a piston reciprocating therein, a fuel passage through said piston, a check valve therein, means for lifting said piston as said throttle is opened, a fuel outlet from said cylinder located so as to be covered by said piston when the throttle is closed, a second fuel outlet located in the upper part of said cylinder, an air entrance into said second fuel outlet both of said fuel outlets being adapted to discharge into said mixture chamber.

10. Accelerating means for a fioatless self feeding carburetor having a mixture chamber, a mixture outlet, and a throttle therein, comprising a substantially vertical cylinder, a piston reciprocating therein, a passage through said piston, a check valve therein, means for lifting said piston as said throttle is opened, a fuel outlet from said cylinder located so as to be covered by said piston when the throttle is closed, a second fuel outlet located in the upper part of said cylinder, both of said fuel outlets being adapted to discharge into said mixture chamber.

11. Accelerating means for a carburetor having a fuel chamber, a mixture chamber, a mixture outlet and a throttle therein, comprising a substantially vertical cylinder communicating at its lower end with said fuel chamber, a piston reciprocating in said cylinder, a fuel passage through said piston, a check valve therein, means for lifting said piston as said throttle is opened, a fuel outlet from said cylinder located so as to be covered by said piston when said throttle is closed, a second fuel outlet located in the upper part of said cylinder, an air entrance into said second fuel outlet, both of said fuel outlets being adapted to discharge into said mixture chamber.

12. Accelerating means for a carburetor having a fuel chamber, a mixture chamber, a mixture outlet and a throttle therein, comprising a substantially vertical cylinder communicating at its lower end with said fuel chamber, a piston reciprocating in said cylinder, a fuel passage through said piston, a check valve therein, means for lifting said piston as said throttle is opened, a fuel outlet from said cylinder located so as to be covered by said piston when said throttle is closed, a second fuel outlet located in the upper part of said cylinder, both of said fuel outlets being adapted to discharge into said mixture chambers.

13. A floatless self feeding carburetor comprising a balanced air valve, a primary air passage controlled thereby, a fuel entrance, a fuel supply passage leading therefrom to said primary air passage on the outlet side of said air valve, means responsive to the flow of fluids in said fuel passage for opening said air valve, means directly responsive to the pressure in said fuel entrance for admitting more or less air to said fuel passage.

14. A carburetor having a mixture chamber and a balanced air valve, a primary air passage controlled by said air valve and leading to said mixture chamber, a fuel entrance, a fuel supply passage leading therefrom to said mixture chamber, a movable obstruction in said fuel passage movable by fuel flowing in said fuel passage and connected to said air valve for moving said air valve, an air passage admitting a relatively small quantity of air to said fuel passage on the upstream side of said obstruction.

15. A carburetor having a mixture chamber and a balanced air valve, a primary air passage controlled by said air valve and leading to said mixture chamber, a mixture outlet, a. throttle valve therein, a fuel entrance, a fuel supply passage leading therefrom to said mixture chamber, a movable obstruction in said fuel passage, a relatively small air passage leading to the upstream side of said fuel passage, a second movable obstruction in said air passage, said second obstruction being connected with the first obstruction and with the balanced air valve, throttle controlled means for obstructing the air flow to said air passage when the throttle is closed.

16. A carburetor as described in claim 15 and having two tapered passages in which the two obstructions are moved by the flow of fluid therethrough.

17. A carburetor having a mixture chamber and a balanced air valve, a primary air passage, controlled by said air valve and leading to said mixture chamber, a mixture, outlet, a throttle valve therein, a fuel entrance, a fuel supply passage leading therefrom to said mixture chamber, a movable obstruction in said fuel passage, a relatively small air passage leading to the upstream side of said fuel passage, a second air passage also leading to the upstream side of said fuel passage, a second movable obstruction in said second air passage, both of said obstructions being connected with the balanced air valve, throttle controlled means for obstructing the air flow to said second air passage and for admitting the air flow to the first air passage as the throttle is closed,

18. A carburetor as described in claim 17 and having two tapered passages in which the two obstructions are moved by the flow of fluids therethrough.

19. In a carburetor having a mixing chamber and an air entrance leading to said mixing chamher, a fuel nozzle discharging therein, a floating obstruction in said fuel nozzle, a balanced air valve operatively connected to said obstruction, said air valve being adapted to control the air entrance to said mixing chamber, said obstruction adapted to open said air valve as the fuel flow increases due to decrease of pressure in said mixing chamber and a corresponding increase of fuel flow through said nozzle.

20. In a carburetor for internal combustion engines, a mixing chamber, means for controlling the delivery of air to said mixing chamber including an air valve responsive to the suction in the mixing chamber, means for delivering fuel to said mixing chamber from a source of fuel supply, and means including a diaphragm directly responsive to the fuel level in said source for controlling said air valve to provide for progressively closing said valve as said fuel in said source becomes lower- 21. In a carburetor having an air entrance, an air valve therein, a mixing chamber leading out of said entrance, a variable lift fuel supply means connected to said mixing chamber through a fuel passage, means for opening the air valve responsive to an increase of suction in the mixing chamber, and means including a diaphragm directly responsive to an increase of lift in the fuel supply means for closing said air valve.

22. In a carburetor, a primary air entrance having an air valve therein, a mixing chamber leading out of said entrance, a variable lift fuel supply means connected tosaid mixing chamber through a fuel passage, a secondary air entrance connected to said mixing chamber through an air passage, means responsive to flow of air through said second air passage for opening said air valve, and means responsive to an increase in lift in the fuel supply for closing said second air entrance.

23. In a carburetor for internal combustion engines, a mixing chamber, a primary air entrance for delivering air to said mixing chamber including an air valve, means for delivering fuel to said mixing chamber from a source of fuel supply, a secondary air entrance connected to said mixing chamber through an air passage, means in said air passage responsive to flow of air therethrough for opening said air valve, and means responsive to the fuel level of said source for progressively closing said second air entrance as said fuel level becomes lower to control the opening of said air valve.

WILFRED O. CHASE. 

